The present invention relates to an endoscope apparatus and, more particularly, to an endoscope apparatus for observing a body cavity by using a solid-state image sensor.
A conventional endoscope apparatus having a solid-state image sensor inside a distal end of an endoscope is known. In an apparatus of this type, an optical image formed by an objective lens system provided inside the distal end of an insertion section is converted to an electrical signal by an image sensor. The electrical signal is then signal-processed and displayed as an image on a monitor. With such an endoscope apparatus, the optical image can be stably transmitted compared to the case of an endoscope using an image guide consisting of a bundle of optical fibers. Moreover, the image can be simultaneously observed by a group of people.
Conventionally, an observation window and an illumination window are provided at a distal end portion of the insertion section of the endoscope, and the illumination window is formed at the leading end side of the observation window in the insertion section. An objective lens system is connected to the observation window through a prism and a solid-state image sensor is provided to oppose the objective lens system. An end of a light guide consisting of a bundle of optical fibers opposes the illumination window and the light guide extends to a proximal end of the insertion section therethrough. In the endoscope of this structure, the image sensor and the light guide are located on an identical cross section of the insertion section, i.e., the image sensor and the light guide are aligned along the radial direction of the insertion section. Therefore, the outer diameter of the insertion section is determined by the sum of the height of the image sensor and the diameter of the light guide. As a result, it is difficult to decrease the diameter of the distal end of the insertion section, and the patient experiences severe discomfort when the insertion section is inserted into a body cavity.